1. Field of the Invention
The present invention relates to surround sound decoding and distribution techniques.
2. Description of the Related Art
Multichannel audio reproduction typically uses a plurality of loudspeakers distributed around a listener, or group of listeners, to convey a sense of immersion or envelopment from a reproduced audio recording or soundtrack or an artificially rendered acoustic event. Multichannel audio was first popularized in movie soundtracks. Movie theaters use a network of loudspeakers distributed throughout the performance space to surround the audience. Multichannel audio has also become popular in homes with the advent of multichannel movie and music soundtrack recordings available on DVD and Blu-ray discs and interactive multichannel soundtracks from gaming consoles and personal computers.
Multichannel audio is often compressed such that the amount of data required to accommodate a high quality soundtrack reproduction is sufficiently reduced to fit on a given physical storage medium or to allow for streaming of that data within a given bitstream bandwidth. Such compression schemes include Dolby Digital or DTS for DVD, Blu-ray disc and HDTV. These encoded data streams are usually passed to an external decoder on a home theater receiver and the decoded PCM soundtrack is directed by wire to multiple output channels for distribution around the listening room. Multichannel audio can also be produced and mixed on the fly by console or PC gaming engines. Multichannel audio can also be created through a special decode of matrix-encoded stereo soundtracks using algorithms such as Dolby Pro Logic or algorithms based on the theory outlined in U.S. patent application Ser. No. 12/246,491. A multichannel soundtrack can also be produced by ‘upmixing’ a traditional stereo soundtrack to a multichannel mix using algorithms such as Creative CMSS-3D Surround, DTS Neo 6 and SRS Circle Surround.
The multichannel audio signals 102 (transmitted, e.g., over a SPDIF connection) are typically decoded and amplified in a single piece of equipment, typically a home theater receiver 104 or a set-top box that distributes each individual reproduction channel by wired loudspeaker connection 106, as shown in FIG. 1. The majority of newer multichannel amplifiers available today will support up to a maximum of 7.1 channel output (i.e., 7 main loudspeaker channels and one subwoofer channel). Newer wireless technologies allow for the wireless transmission of audio channels using, for instance, the Bluetooth Advanced Audio Distribution Profile (A2DP). This approach alleviates the need for unsightly wiring connecting the main amplifier to the rear loudspeakers.
Often, the data rate of home wireless audio transmissions is limited and only allows for the transmission of two channels of audio data, for instance. Hence, in many wireless multichannel audio playback solutions, only a subset of the audio channels can be transmitted wirelessly, while the other channels require wired loudspeaker connections.
In any wireless multichannel audio reproduction system where audio channel signals are transmitted discretely, increasing the number of wireless loudspeakers requires a proportional increase in wireless transmission bandwidth. This ultimately limits flexibility and scalability in wireless multichannel audio systems. Furthermore, increasing the number of channels may require replacing common components such as signal processors, digital-to-analog converters, or amplifiers by special (non generic) components, and require the shared multichannel decoder or amplifier unit to have larger cost, power consumption and size. Therefore, improved techniques and systems for multichannel audio decoding and distribution are needed.